ABSTRACT The perinatal period, defined as the period from pregnancy through the first postpartum year, is a critical time for weight management intervention and provides a unique opportunity to understand factors associated with weight and eating behaviors. In response to PAR-16-304, we propose to leverage our ongoing efforts to evaluate sequences of weight management across the perinatal period by evaluating the contribution of behavioral phenotypes to perinatal obesity. Specifically, we propose to examine the link between impulsive phenotypes and perinatal weight. Impulsive phenotypes are associated with higher body mass index, greater weight gain over time, and poor response to weight management interventions. The effects of impulsive phenotypes on weight changes also are bidirectional. However, the role of impulsive phenotypes on weight trajectories over the perinatal period, and how these phenotypes may affect response to perinatal weight interventions, is unknown. Our work, and that of others, has documented strong links between weight and impulsive phenotypes characterized by: (1) disinhibited behavior, (2) attentional deficits, (3) impulsive decision- making, and (4) cognitive inflexibility, though it remains unclear whether and how these impulsive phenotypes predict weight trajectories and eating behavior over the perinatal period or response to perinatal intervention. Accordingly, we plan to assess these impulsive phenotypes among women with overweight or obesity enrolled in a perinatal weight trial. Women with overweight or obesity before pregnancy are currently being recruited and followed in a sequential multiple assignment trial designed to evaluate sequences of perinatal weight management interventions associated with improved maternal weight and health one year postpartum (R01HL132578). Women are enrolled at the beginning of prenatal care and randomly assigned to intervention that addresses the unique challenges of weight during pregnancy or a comparison condition involving treatment as usual. At delivery, women again are randomized to postpartum weight intervention or treatment as usual. We propose to add behavioral tasks and questionnaire assessments of impulsive phenotypes and eating behaviors to capitalize on the data collected in this parent trial. The specific aims are to (1) examine impulsive phenotypes as predictors of perinatal weight trajectories across the postpartum year, and (2) evaluate relationships among impulsive phenotypes, perinatal interventions and weight loss outcomes and eating behaviors. We also will explore the joint trajectories of weight and impulsive phenotypes from pregnancy through 12-months postpartum. Assessing impulsive phenotypes within a study of perinatal weight intervention will enhance the understanding of behavioral and cognitive factors associated with weight trajectories across the postpartum year. These data will support efforts to personalize weight management interventions and contribute to the development of novel behavioral perinatal interventions to improve longer-term health.